Fuels for spark-ignition engines must conform to stringent specifications regarding their volatility characteristics to ensure satisfactory operation of combustion engines. The fuel must contain a large enough fraction of highly volatile components for good cold starts of the engine, but the volatility must not be so high as to impair operation and starting, or during driving, when the engine is warm.
The volatility has a major influence of the wall-wet dynamics in the cylinders in for example port-injected gasoline engines. A fuel having different fuel volatility will result in a changed air-to-fuel ratio, which may lead to a non-desired combustion.